source of toxin was living blowflies which, pre- 

 sumably, had become toxic by feeding on the car- 

 casses of birds that had died from botulism. 



In experiments with flies fed on suspensions of 

 Clostridium hotul'mum cells of known toxicity, it 

 was found that the oral administration to a duck 

 of the ground tissue suspension of 1.5 tlies could 

 induce marked symptoms of botulinal intoxication. 

 The susceptibility of individual birds varied but, 

 in general, an increase in the dose of fly tissue in- 

 creased the severity of the symptoms. 



The results of two experiments suggested that 

 the ingestion of type C toxin by blowflies enhances 

 its toxicity for ducks. Study is under way to de- 

 termine whether the toxin molecule is broken down 

 into two or more toxic fragments by the digesti\e 

 enzymes of the fly or the apparent enliancement 

 represents only an accumulation of toxin in the 

 fly's tissues. The experiments will be extended in 

 order to learn whether a similar enhancement of 

 toxicity occurs within the bodies of aquatic 

 invertebrates. 



Chemical method of controlling botutism. — Sev- 

 eral attempts were made to produce "outbreaks" 

 of botulism in exi)erimental ducks conflned within 

 plastic rings on the marsh. Progress has been 

 hampered by technical difficulties, particularly 

 flooding of the ring by wind action. 



The experimental data are still too few to sup- 

 port conclusions. In two tests, however, inipro- 

 tected birds in the DDT-treated rings died, while 

 their antitoxin-protected ring-mates remained 

 healthy. None of the birds in the malathion- 

 treated rings or the control rings were afl^ected. 

 Since the unprotected birds in the DDT-treated 

 rings were found dead, a diagnosis of botulism 

 could not be made; but there was no gross patho- 

 logical evidence of other diseases. The fact that 

 the unprotected birds in the malathion-treated 

 rings were not affected may be a manifestation of 

 the inhibitoi-y effect of the pesticide on Clo-strldiiDu 

 hotulinum. which has been demonstrated in the 

 laboratory. 



Dijica-He stiuliex at Patu.rent. — A gi-owing activ- 

 ity in diagnostic services of the disease laboratory 

 at the Patuxent Wildlife Eesearch Center was 

 evident in 19(12. Most calls were from U.S. Game 

 Management Agents, Refuge personnel, and biolo- 

 gists of State game agencies. Diagnostic findings 

 from specimens submitted provided opportunity 

 to recognize some of the important wildlife dis- 

 ease problems in the country. Thus, a.ssistance 



Study of reproductive tracts of doe white-tailed deer 

 in Iowa has indicated breeding by most female fawns 

 and a high productivity rate for the species on much 

 of its Iowa range. (Photo by Iowa Cooperative Wild- 

 life Research Unit) 



given to the State of North Dakota led to a diag- 

 nosis of hemorrhagic virus disease as the chief 

 cause of a large dieofl' in deer. Similar assistance 

 to other States led to a diagnosis of botulism in 

 ducks in Maryland and Michigan. Increasing 

 evidence indicates that losses of waterfowl from 

 this disease are not confined to western alkali 

 lakes. Several deaths of waterfowl along the 

 mid-Atlantic Coast in the spring of 1062 were 

 attributed to aspergillosis, a common fungus in- 

 fection of the respiratory system. The causative 

 organism was also oliserved in a cowbird, and was 

 the cause of losses in several captive herring gulls. 

 Collaboration with luologists in a number of 

 State game agencies provided data for a survey of 

 the occurrence of trichomoniasis, a parasitic infec- 

 tion of the throat of mourning doves. Samples 

 (throat swabs) from ;^,098 birds from 22 States 

 were collected from nestlings, flying young, and 

 adults before and during the 1962 hunting season. 

 Of the total, 7.6 percent were infected, and nest- 

 lings were more frequently infected than the ad- 

 ults. Very few of the birds in hunter's bags 

 showed infection. The highest prevalence of the 

 disease was in June and August, with 22.2 percent 

 (the highest noted) of. the August sample show- 

 ing the disease. Trichomonads were present in 

 all States adequately sampled. The infection is 

 readily passed from parent to ofl'spring in the 

 normal process of feeding the young; thus, the 

 nestlings of infected parents are usually diseased. 

 A further cycle occurs in older birds, and biolo- 

 gists working on the problem hypothesize that 

 contaminated food or water is the source of this 



49 



